The prior art is as follows, concerning the method for examining or processing structural surfaces at the molecular or atomic level and the method for detecting DNA base arrangement:
(1) The method for examining structural surfaces at the molecular or atomic level:
For example, an X-ray microanalyser measures ratio of existing atoms, spectroscopic means analyze the kinds of chemical bonds, and a chemical reactor distinguishes the types of chemically sensitive groups. A scanning tunneling microscope (STM) directly examines structural surfaces to distinguish individual atoms by measuring tunneling current variations corresponding to the atoms in structural surfaces. This method can detect distribution of impurities in in a semiconductor substrate. The information acquired by such means clarify surface structure.
(2) The method for processing structural surfaces at the molecular or atomic level:
A chemical reactor can process surface structure. A common method is to repeat operations to change the structure of partially unprotected surfaces, using a protecting group; removing it to another part to react another unprotected structure and so on. As stated in "Nature" Vol. 344 (5) page 524 (1990), for example, a scanning tunneling microscope (STM) has been used to process surface structure. An individual Xenon molecule has been successfully placed side by side on a nickel substrate with an atomic level of accuracy.
(3) The method for detecting DNA base arrangement:
Recent biotechnology studies have produced living organisms with superior useful characteristics by genetic engineering. Organisms have been engineered to produce useful substances more efficiently.
In the biotechnology field, it is important to know the base arrangement of DNA (Deoxyribonucleic acid) which controls characteristics of a gene.
Certain methods for detecting DNA base arrangement are known.
FIG. 16 to FIG. 18 show a recent conventional method for detecting DNA base arrangement. FIG. 16 is a conceptual drawing which shows a single stranded DNA template used to produce double stranded DNA using DNA polymerase and four kinds of nucleotides. As is shown in FIG. 16(a), the DNA is treated in alkali and changed to single stranded DNA 309. Then, as is shown in FIG. 16(b), primer 310 including radioactive .sup.32 p is added to the single stranded DNA 309. This solution in which four kinds of Deoxyribonucleotide tri phosphoric acid 311 (common name of this molecule is nucleotide; they are (A) including adenine as a base, (T) including thymine, (C) including cytosine and (G) including guanine) and DNA polymerase are mixed to produce a complementary base pair (to hydrogenate as base pairs thymine with adenine, and guanine with cytosine uniquely) on single stranded DNA 309, making double stranded DNA 312, as in FIG. 16(c).
A small quantity of deoxyribonucleotide triphosphoric acid is permuted by hydrogen from the hydroxyl group of the 3'-site of the deoxyribose nucleotide.
Such a modified nucleotide which is taken in by DNA can not be added to the next nucleotide and the reaction stops here. Consequently as shown in FIG. 17, after a certain period of reaction, a small quantity of a modified nucleotide 313, adenine, is taken into a strand in a random like manner, similar to a monomer in a random polymer, which produces various types of double stranded DNA, with adenine at one end, resulting in double stranded DNA having different lengths.
FIG. 17 is a drawing which models the method for making various types of double stranded DNA having adenine at one end and varying in length. 314, 315, 316 and 317 in FIG. 17 show nucleotides hydrogenated with a complimentary base of single stranded DNA 309.
FIG. 17(a) shows each component before reaction. FIG. 17(b) shows variable length DNA having adenine at one end, obtained by reaction. FIG. 17(c) shows three different lengths of double stranded DNA having adenine at one end.
In the same way, repeated operations for the other three kinds of nucleic acid bases can produce various types of double stranded DNA having adenine, cytosine, thymine or guanine at one end.
Four kinds of DNA solution 318, 319, 320 and 321 as shown in FIG. 18 are electrophoresed in four lanes, and the pattern 322 as in FIG. 18 is measured by autoradiography, so the original DNA base arrangement can be detected. An arrow 323 in FIG. 18 shows the direction of the electric field during electrophoresis. However, the problems of the prior art for examining or processing surface structure or detecting DNA base arrangement are as follows:
(1) On examining surface structure at the molecular or atomic level:
An X-ray microanalyser and a spectroscopic or chemical analyser are useful. However, a spectroscopic analyser can not examine surface structure smaller than the wavelength of light and the operation is complicated. STM surface structure analysis is possible only when there are few atoms and impossible when the surface substance has many kinds of atoms in composition. That is, if there are many kinds of atoms, it is difficult to distinguish between atoms, because an electron belonging to an atom is influenced by an electron cloud of a neighboring atom.
(2) On processing surface structure at the molecular or atomic level:
A chemical reaction processing method has a problem that although only a part of the surface structure should be changed, all reaction sites are reacted. Therefore, a protecting group is needed to cover the reaction sites. This method is impossible without a protecting group. Moreover, it is difficult to process only a microscopic region. For processing surface structure of many kinds of atoms by STM at the molecular or atomic level, an STM probe must carry the atoms. However, as the kinds of atoms to be carried are limited, it is difficult to process surface structure by STM.
(3) On detecting DNA base arrangement:
Problems of known methods are: (a) A lot of DNA is needed, (b) Radioactive .sup.32 P to be used needs a special facility to protect from radiation sickness. (c) The shelf life of .sup.32 P is as short as 14 days so that reagents have to be continuously replaced.